Shears are often used to cut things. Shears, whether they be scissors for cutting paper or large hydraulic shears for cutting metal or other materials, operate on similar principles. Two relatively flat surfaces move past each other and are close enough to slide against each other. The material to be cut is located between the two surfaces and fails in shear causing the material to be cut.
While the system works well for cutting a variety of objects, problems can develop. For example, simple paper cutting shears may not always cut if the paper is allowed to move substantially parallel to the shears and the two shearing surfaces move past the paper. The problem of material sliding down the shearing surface rather than being cut is not limited to paper cutting shears but happens in shears of all types. This can cause problems not only with small paper cutting shears but large hydraulic shears.
For example, when using large hydraulic shears to cut objects such as metal, if the shears are worn, not properly adjusted, ill designed, or for variety of other reasons, the shears may not cut. Rather, in such instances, the metal may smear down the sides of the shear surfaces. This can cause a situation where the metal that was to be cut jams the jaws of the shear. It can even cold weld itself to the shearing surfaces on the shear jaws. This may result in a substantial delay while the operators of the hydraulic shears may need heavy tools to remove the fouling from the shear jaws.
Heavy-duty shears such as hydraulically activated shears often use shear plates that are set within shear plate pockets. The shear plates are often removable from the shear jaws so that the shear plates (which are a high wear part) may be rotated, removed for maintenance or replaced when they become worn. Shims can provide a desired positioning of the shear plate within the shear plate pocket. Traditionally, shear plates are set to be at a neutral position or, in other words at 0 angle with respect to the opposing jaw. This may be referred to as a neutral camber. If the shear plates having negative angle, sometimes referred to as a negative camber, they may actually pull the workpiece to be sheared toward the jaws or create other problems.
One example sheer is described in U.S. Pat. No. 6,926,217. This patent describes a shear jaw where a cross blade located at an end or tip of the jaw is located at an acute angle between 1 and 30 degrees. While this cross blade may assist in snipping material at the end or tip of the jaw, it does not address the problems associated with the cutting surfaces located at the sides of the jaw. The sides of the jaw is where a majority of the cutting or shearing often occurs. As a result, the embodiment illustrated in this patent does not specifically address the problems described herein.
In addition to these problems, substantial force may be required to cause some materials to be sheared. As result, shears are very robustly built and operated by robust hydraulic systems. Furthermore, shears often are called upon to provide many cutting operations. As result, the shear surfaces or edges that help define the shear surfaces may become rounded or otherwise dull.
Accordingly it would be desirable to provide a set of shears that can provide any, some, or all of the following characteristics: more reliably cut material rather than smearing it along the shear surfaces, reduce the amount of force required to cut material, and provide many cutting operations before needing any adjustments.